He said: “The question is, what did his photo enhancing software uncover?

“Did it find something that NASA was hiding in the background of the photo as they always do in the Martian photos?

“Is this a city in the background or simple photo artefacts? In my opinion, I believe we are seeing a city.

“There is no way to clarify this so it is pure speculation but I think it is wild that if these are in fact vehicles, it wouldn’t surprise me if these were some kind of structures behind it.”

An enhanced image seems to show a city in the background (Image: YOUTUBE)

Some were in agreement with Chris’s theory.

One person said: “it’s either buildings on Mars or it’s Earth made too look like Mars. Wouldn't surprise me either way!”

Another added: “Those are vehicles and structures in the background. I don't envy the humanoids OR other alien beings that call Mars home. It looks like the Martians got a VERY hard knock life indeed.”

However, others were not so convinced.

One person stated: “I'd like to think that this is real, but I'm not convinced by these 'enhanced' background images to be honest.”

Sceptics and NASA would say the ‘city’ and other similar findings are just the effects of pareidolia – a psychological phenomenon when the brain tricks the eyes into seeing familiar objects or shapes in patterns or textures such as a rock surface.